Working principle of Taeda sludge+calcium drying system

　　With increase of waste water treatment plants and development of waste water treatment technology, there are more and more sludge produced during waste water treatment process. Although there existing many disposal methods, like thermal drying, composting and incineration, basic investment and running cost are pretty high. Meanwhile, by-products with high pollution like dioxin. Taeda® CAO alkaline stabilization drying method can realize sludge drying, solicitation and bacterium elimination with low investment cost, quick result and stable disposal effect. This method is more suitable for further treatment of dewatered sludge from small and medium sized waste water plants.
（1）Basic principle of CAO drying system 
　　Mix sludge with fine lime uniformly, following chemical reaction between lime and moisture in sludge.
　　1kgCaO+0.32kgH2O---->1.32 kgCa(OH)2+1177kJ

　　According to this reaction, there will be 0.32kg water combined into calcium hydroxide for feeding 1kg calcium oxide. Heat produced from this reaction can evaporate about 0.5kg water. Quick lime reacts with water and produces calcium hydroxide. After this reaction, quick lime will further react with heavy metal in sludge and other compound matters. Final result is:

A.Further dewatering process: Moisture is reduced to 20% to 65% from 80% to 85% （decided according to lime amount）.
B.Ｋill bacterium, rise of temperature of PH value has bacterium elimination function, which can guarantee sanitary safety during utilization and disposal process.
C.Passivate heavy metal ions, add certain amount of calcium oxide to make sludge alkaline. Partial metal ions in sludge will combine with lime and form harmless compounds to reach heavy metal ions passivation aim.
D.Ｍodification and granulation, improve storage and transportation condition; Avoid secondary fly ash and leak of leachate.
E.Semi-dry and solidification, effectively reduce moisture content, provide convenience for reutilization and landfill.
F.Because moisture is evaporated, although extra amount of lime is added to whole system, system total weight doesn’t increase too much.

（2）What are the application ranges of dried sludge?
　　Moisture of sludge can be dried to lower than 50% and transverse shear force is increased. Dried sludge can be used for building materials, coordinated incineration in cement plants, land use (such as landscaping and soil improvement), sanitary landfills and etc. It conforms to the "low carbon economy, safe and environmental friendly, sound and reliable" plan. It is a feasible, usable and reliable sludge treatment technology.

CAO sludge drying system combines advantages of both thermal drying and alkaline stabilization drying.

　　There are many methods for sludge treatment and disposal at home and abroad. Generally applied methods are concentration, digestion, dehydration, drying, effective utilization (mainly for agricultural use), landfill and incineration. Or combines some among above methods for disposal. Different treatment methods have different pre-treatment requirements. In fact, some pre-treatment requirements are part of this treatment method. Ultimate final uses of sludge contains partial, full utilization as resources or return to the environment in some certain form. (1) Harmlessness and stabilization: Alkaline stabilization is to add alkaline substances such as lime or cement kiln dust to sludge so that to keep the sludge pH> 12 for a period of time. Make use of strong alkalinity and a large amount of heat released by lime to kill pathogens, reduce malodor and passivate heavy metals. After treatment, sludge can be directly applied to farmland. There are two major treatment methods for alkaline stabilization. One is to quickly dry sludge by mechanical turning or other methods after alkaline stabilization. The other is to compost after mixing alkaline materials. (2) Thermal drying: Thermal drying is to make use of heat to dry sludge. Dried sludge is in the form of granules or powder and volume is only 1/5 to 1/4 of original volume. Because moisture content is below 10%, activeness is completely inhibited which helps avoid mold and odor and provides convenience to storage and transportation. High-temperature sterilization effect during the thermal drying process is very thorough. Product can fully reach sanitary index and sludge performance is comprehensively improved. Final product can be used as an alternative energy source or for land use. TAEDA thermal drying equipment is characterized by high automation level, good safety performance and high heat conversion efficiency. Taeda® CAO technology alkaline stabilization drying system combines advantages of both thermal drying and alkaline stable drying technology. Discharged sludge holds good index and conforms to industrial standard. 

Technical features and application range:

　　Widely applied for disposal of dehydration sludge from small and medium sized waste water treatment plants. Especially suitable for sludge produced by mixing treatment of household sewage and industrial waste water. It has high sterilization and deodorization capabilities. Whole system is fully enclosed. It is featured in environmentally friendly and good operation conditions, which makes it suitable for sensitive sewage treatment plants in the surrounding area; Whole system occupies a small area and is flexible in layout. It can be constructed in plant without dismantling. Shut down existing dehydration and especially suitable for projects with limited land use. The system is reliable, simple management and needs less maintenance. It can be integrated with the existing sludge dewatering system without increasing burden of management and personnel. Project construction period is short. Requirements for harmlessness, stabilization and drying of sludge can be quickly solved, especially suitable Emergency projects with tight construction period and urgent task demand. Both investment and operating cost are low, suitable for upgrading and amendment of existing sewage treatment plants and disposal requirements for harmless, stabilizing and drying of sludge. Meanwhile, it can be used as a temporary replacement for incineration system and used for stabilization disposal of sludge after anaerobic digestion.

Performance Guarantee and Implement Period:

　　After disposed by Taeda CAO sludge drying system, index of discharged sludge are shown as below:

　　Taeda CAO sludge+calcium alkaline stabilization drying technology makes use of the reaction between quick lime and water to form high temperature and high alkaline environment. While evaporating moisture and realizing deep dehydration aim, harmful pathogen and bacterium will be killed. Partial heavy metal is passivated and odor is removed. Finally, whole process realizes drying, harmless and stabilization aim. Environment pollution and social concerns caused by dewatered sludge are effectively solved. Thus, normal running of waste water treatment plant can be guaranteed.